A supramolecular chain of dimeric Dy single molecule magnets decorated with azobenzene ligands

Abstract

We report the synthesis, ab initio calculations, magnetic and optical characterization of a Dy^III-based dimeric compound named DyAZO. The dimers self-organize into a supramolecular chain decorated with photo-isomerizable azobenzene ligands. DyAZO displays single-molecule magnet (SMM) behavior. However, ab initio calculations highlight a quite strong admixture of M_J states of the ⁶H_15/2 level of Dy^III ions, the presence of low-lying excited M_J states and antiferromagnetic Dy–Dy dipolar coupling. This favors zero-field fast tunneling. Accordingly the Dy-doped analogue YDyAZO (5.5% Dy doping) displays enhanced magnetic relaxation with a hysteresis that is observed at 0.5 K. The influence of the cis- to trans-isomerization of the decorating azobenzene ligand on magnetic properties has been tested for both solid samples and solutions of DyAZO and YDyAZO. This provides hints for the synthesis of future Dy-based photo-isomerizable molecules.